Dodgers shortstop Manny Machado throws as he falls to the ground, too late to get Oakland Athletics’ Khris Davis on an infield single during the fourth inning of a baseball game Tuesday, Aug. 7, 2018, in Oakland, Calif. (AP Photo/D. Ross Cameron)

OAKLAND, CA – AUGUST 07: Rich Hill #44 of the Los Angeles Dodgers pitches in the first inning against the Oakland Athletics at Oakland Alameda Coliseum on August 7, 2018 in Oakland, California. (Photo by Lachlan Cunningham/Getty Images)

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OAKLAND, CA – AUGUST 07: Manny Machado #8 of the Los Angeles Dodgers celebrates with teammates after scoring in the first inning against the Oakland Athletics at Oakland Alameda Coliseum on August 7, 2018 in Oakland, California. (Photo by Lachlan Cunningham/Getty Images)

Los Angeles Dodgers’ Chris Taylor (3) slides safely into third base ahead of the relay to Oakland Athletics third baseman Matt Chapman during the second inning of a baseball game Tuesday, Aug. 7, 2018, in Oakland, Calif. At left is umpire Jansen Visconti. (AP Photo/D. Ross Cameron)

OAKLAND, CA – AUGUST 07: Austin Barnes #15 of the Los Angeles Dodgers lays down a sacrifice bunt to score teammate Chris Taylor #3 in the second inning against the Oakland Athletics at Oakland Alameda Coliseum on August 7, 2018 in Oakland, California. (Photo by Lachlan Cunningham/Getty Images)

Los Angeles Dodgers’ Chris Taylor (3) is greeted by his teammates after scoring on a squeeze bunt by Austin Barnes during the second inning of a baseball game against the Oakland Athletics, Tuesday, Aug. 7, 2018, in Oakland, Calif. (AP Photo/D. Ross Cameron)

Los Angeles Dodgers’ Cody Bellinger (35) slides safely under the tag of Oakland Athletics third baseman Matt Chapman during the inning of a baseball game, Tuesday, Aug. 7, 2018, in Oakland, Calif. Bellinger went from first to third on a single by Yasiel Puig. (AP Photo/D. Ross Cameron)

OAKLAND, CA – AUGUST 07: Cody Bellinger #35 of the Los Angeles Dodgers is tagged out at home plate by catcher Jonathan Lucroy #21 of the Oakland Athletics in the sixth inning at Oakland Alameda Coliseum on August 7, 2018 in Oakland, California. (Photo by Lachlan Cunningham/Getty Images)

OAKLAND, CA – AUGUST 07: Sean Manaea #55 of the Oakland Athletics pitches in the first inning against the Los Angeles Dodgers at Oakland Alameda Coliseum on August 7, 2018 in Oakland, California. (Photo by Lachlan Cunningham/Getty Images)

Los Angeles Dodgers’ Manny Machado reacts after striking out against the Oakland Athletics during the fourth inning of a baseball game Tuesday, Aug. 7, 2018, in Oakland, Calif. (AP Photo/D. Ross Cameron)

Los Angeles Dodgers’ Justin Turner (10) scores on a single by Cody Bellinger during the third inning of a baseball game against the Oakland Athletics, Tuesday, Aug. 7, 2018, in Oakland, Calif. (AP Photo/D. Ross Cameron)

The Dodgers’ Justin Turner celebrates after scoring a run on a single hit by teammate Cody Bellinger during the third inning of Tuesday’s game against the A’s in Oakland. (Photo by Lachlan Cunningham/Getty Images)

Oakland Athletics second baseman Jed Lowrie (8) throws over Los Angeles Dodgers’ Cody Bellinger (35) to complete a double play during the seventh inning of a baseball game, Tuesday, Aug. 7, 2018, in Oakland, Calif. Yasiel Puig was out at first base. (AP Photo/D. Ross Cameron)

OAKLAND, CA – AUGUST 07: Rich Hill #44 of the Los Angeles Dodgers pitches in the first inning against the Oakland Athletics at Oakland Alameda Coliseum on August 7, 2018 in Oakland, California. (Photo by Lachlan Cunningham/Getty Images)

Oakland Athletics’ Mark Canha (20) comments to home plate umpire Tim Timmons (95) after he was called out on strikes during the sixth inning of the team’s baseball game against the Los Angeles Dodgers on Tuesday, Aug. 7, 2018, in Oakland, Calif. (AP Photo/D. Ross Cameron)

OAKLAND, CA – AUGUST 07: Khris Davis #2 of the Oakland Athletics hits a two-run home run in the sixth inning against Los Angeles Dodgers at Oakland Alameda Coliseum on August 7, 2018 in Oakland, California. (Photo by Lachlan Cunningham/Getty Images)

OAKLAND — The Dodgers have spent four months on research and development. Now they will devote the final two months of the season to field-testing their bullpen in a playoff race.

Dodgers manager Dave Roberts entrusted a one-run lead in the sixth inning to his bullpen on Tuesday night and was rewarded with 3-2/3 innings of one-hit, scoreless relief, securing a 4-2 victory over the Oakland A’s.

The Arizona Diamondbacks and Colorado Rockies both lost Tuesday, allowing the Dodgers to leapfrog back into first place by a half-game over the Diamondbacks and 2-1/2 over the Rockies.

Against the A’s, Dylan Floro, Scott Alexander, J.T. Chargois and Kenley Jansen combined to retire 11 of the final 12 A’s batters, six on strikeouts. The Dodgers never had a lead to protect in the first two games of their weekend series with the Houston Astros. But over the past two games, Floro (two innings), Alexander (2-1/3), Chargois (one) and Jansen (two) have combined for 7-1/3 scoreless innings out of the bullpen.

Of the four, only Jansen did not spend part of his summer with Triple-A Oklahoma City.

“Honestly, guys are starting to step up. I feel like you can see they want it,” Jansen said of the auditions to be his warm-up act. “Three guys who’ve been down to Triple-A. That’s perfect. They want it. They want the ball. They want to take advantage of every opportunity to make a name for themselves.”

Plenty of names were tossed around as the trade deadline approached. The Dodgers did add veteran reliever John Axford. For now, though, Roberts’ circle of trust seems to be made up of Floro, Alexander, Chargois and Jansen.

“Guys are starting to take advantage of some opportunities,” Roberts said. “You look at where we’re using Floro – whether it be in the fifth inning, in the seventh inning, in some leverage spots – he’s really doing a great job. Chargois, ever since he came back from OKC, he’s been dominant. He’s throwing strikes and competing well. And Alexander is doing the same thing. Since he came up he’s been lights out – throwing strikes, getting the ball on the ground when he needs to.

“And Kenley, the last two outings it’s been good to see him be efficient and pitch to all the quadrants. They’re taking advantage. You see the confidence is starting to build with those guys.”

Since returning from an early-season demotion to Triple-A, Alexander has been the pitcher the Dodgers thought they were trading for over the winter. He has a 2.48 ERA since early May, holding batters to a .209 average.

Chargois made his return from Triple-A at the start of July. Since then, he has allowed one run in 10-1/3 innings with 13 strikeouts, one walk and a .147 average against.

Floro made a five-day detour to Triple-A as a way to get a fresh arm in the bullpen following the Dodgers’ 16-inning game in Philadelphia. He has retired all 16 batters he has faced since then, six on strikeouts.

“When you’re playing with the division close and every game is obviously important, there’s a little bit of (playing) the hot hand,” Roberts said. “And I see the confidence. I see the pitch-making. So those guys have earned it.”

They made a lead stand up that was built on spare parts – a run-scoring ground out in the first inning, a safety squeeze bunt by Austin Barnes (who nearly pulled it off a second time) in the second and a two-out, two-strike RBI single by Cody Bellinger in the third.

Matt Kemp drove in an insurance run in the seventh after Joc Pederson doubled. Kemp dumped an RBI single just over the infield and onto the grass in right field – only his second hit in his past 45 plate appearances.

Bill Plunkett has covered everything from rodeo to Super Bowls to boxing (yeah, I was there the night Mike Tyson bit Evander Holyfield's ear off) during a career that started far too long ago to mention and eventually brought him to the OC some time last century (1999 actually). He has been covering Major League Baseball for the Orange County Register since 2003, spending time on both the Angels and Dodgers beats.